must be the switch mode regulator that they are using
I am certain it is. David Gersic (Zaccaria Guru) gave me a serve for NOT using a switching design in my new display power supply (shown here http://www.homepin.com/other.html).
I explained to him that they are not always the best answer. Sometimes cheaper, simpler, run cooler BUT not the best choice under all conditions.
I have chosen the standard, simple, no special parts, easy to fix series regulator for this project.
I read this post earlier and was going to ask if it used a switching regulator. Would absolutely be the source of the noise..
